Various designs of wall fastening have been in existence for a number of years. An advanced type is described in U.S. Pat. No. 4,500,238. It comprises a sword-like anchor made of thin sheet metal, having two spreadable pointed flat blades for easy insertion in a wall. After insertion, the blades are spread apart by driving a fasteners member, typically a screw, thereinbetween to provide resistance to withdrawal.
The ability of the anchor to enter the wall, and its holding power depend to a degree on the material used for the anchor, among other factors. Thus it is desirable to employ thin sheet metal of high strength, such as for example, spring steel metal or the like. However, to facilitate manufacturing, it is desirable to use a soft malleable material which can be easily shaped, cut and folded with conventional dies.
To satisfy both requirements, a soft malleable sheet of metal is first used to cut, shape and fold to produce the desired shape for the anchor. The anchor is then heat treated by heating and quenching then tempering at an appropriate temperature in accordance with well known technology to harden the metal. During the quenching step it has been found that the folded article under the treatment stresses has a tendency to resume its original unfolded shape. The result of this tendency is a partial separation of the blades especially near the tip thereof which renders the article inferior for its intended purpose and reduces productivity.
There is thus need for an inexpensive solution to the aforementioned problem and a need for an inexpensive way to hold the blades of such anchors in contact with each other during the hardening and particularly the quenching process.